- Small plastic bottle
- Vinegar (or lemon juice)
- Baking soda / bicarbonate of soda
- Balloon
- Teaspoon
- Two funnels
Method
- Put 1cm of water into the bottle, and then add about 2 cm of vinegar
- Stretch the neck of the balloon
- Use a funnel to put 2 teaspoons of baking soda into the balloon
- Place the balloon over the mouth of the bottle, making sure none of the baking powder falls into the bottle
- Lift the end of the balloon and pour all the baking powder into the bottle in one go
- Shake the bottle well and then watch the balloon inflate all by itself
What is going on
There is a reaction between the base (baking soda) and the acid (vinegar). This reaction produces a gas called carbon dioxide or CO2 (one of the gases we breathe out). The gas produced by the reaction rises up and escapes through the plastic bottle, it doesn't however escape the balloon, pushing it outwards and blowing it up.
Caution – the more vinegar and baking soda used, the more extreme the reaction.